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Re: Light Bulb Dilemma

To: Richard Beels <beels@technologist.com>
Subject: Re: Light Bulb Dilemma
From: Susan and Mark Miller <marknsuz@pacbell.net>
Date: Wed, 20 Feb 2002 19:49:29 -0800
Richard Beels wrote:

> So, what would make the voltage in the one room too high?   As I said, I
> don't remember the actual voltage but when I was other there last week, it
> didn't jump out at me as too high.  But if the voltage was too high, it
> would be high for the whole house and that would be frying all the bulbs,
> right?

The voltage is the difference between the line and its return.  In a house wired
for 220/240 VAC single split phase this is typically one of the two phases and 
the
neutral.  The neutral is also typically bonded (connected) to ground at one 
point
in the house, most often at the breaker box/meter.  If there is either an
insufficient ground or a bad connection between the neutral and ground it is
possible for the neutral to 'move around' as referenced to ground.  It could 
also
happen that the neutral in just that circuit is not well connected, perhaps due 
to
a poor connection or as mentioned in other responses there could be a poor
connection between aluminum and copper wiring.

If there are heavy loads on the other phase then the neutral could be 'dragged'
towards that phase, and therefore away from the one driving the lighting.  This
would be seen as an overvoltage at the lamps.

Picture two sinewaves 180 degrees out of phase; this looks like a row of 
footballs
lined up point to point.  A perfect neutral would be the flat line right down 
the
middle.

If it's not flat and down the middle it could either give an overvoltage 
condition
or one where the bulbs sees short spikes of higher voltage.  Both could be bad 
for
the bulbs.

It might or might not affect the rest of the house, based on whether the other
neutrals are OK or not.  It's possible that the rest of the lighting is on the
other phase as well.

Or not.....

Mark Miller

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